Screw-type jacks heretofore employed for supporting a trailer tongue, when the trailer is disconnected from the hitch of a towing vehicle, have been provided with a mounting flange or support plate welded to the body of the jack. The mounting flange is generally bolted to the tongue of the trailer and a support leg having a foot or caster on the lower end is moved vertically by rotating a screw in the jack.
When trailers are manufactured and then shipped to dealers for resale, jacks generally are not installed on the trailers to facilitate stacking the trailers for shipment. Dealers sometimes fail to install the jack properly after the trailers have been delivered.
Screw-type jacks developed heretofore have not been constructed to permit movement of the jack quickly to an initial position wherein the foot or caster engages the ground and to permit subsequent rotation of the screw only for elevating the tongue of the trailer the distance required for disengaging the coupler on the trailer tongue from the hitch on the towing vehicle.
Further, a thrust washer is generally butt welded to the upper end of the outer tube of screw jacks to prevent vertical movement of the screw through the outer tube. The butt weld securing the thrust washer to the upper end of the outer tube of the jack generally is capable of carrying only about 12,000 to 16,000 pounds of force, which is inadequate for certain applications. Handles on screw jacks heretofore devised required a separate locking mechanism to prevent rotation of the elevating screw when the jack was not in use.
In addition to the aforementioned limitations, the present caster and foot designs used on jacks are not very versatile; they are not interchangeable between different sized jacks nor can they be used to provide firm support on uneven or non-level surface conditions.
A need exists for a screw-type jack and support which eliminate these deficiencies.